In a defensive scenario the opposition has created the situation. By escalation, I mean to change one’s own posture or response. I can be a victim. I can attempt escape (sometimes wise). Or I can use force. I’m not intending to suggest that you create the situation to begin with if that is what it appears. Otherwise, I will grant that there are gun owners who only shoot paper, and only intend to ever shoot paper. And some few who delude themselves that they might be able to incapacitate or maim instead of kill. But at the end of the day, it has one purpose – to kill.
“As any well-trained gun owner knows, firearms are an option when all other options fail.” I have no idea who trained you. But this is not what a coherent escalation looks like. If you are escalating to force, you can and should employ a firearm if you have it. Immediately. Tasers, knives, ‘martial arts’, are, frankly, backups only – and relatively poor ones. Once you have closed to knife or martial art range the firearm is potentially worse than useless – it can be taken from you and used against you. A well-trained gun owner knows that a gun has the power to end life and that he or she needs to come to terms with the potential for ending a life. You must be willing to do so to defend certain things. Know what those things are. Know how to evaluate when you are willing to make this choice. Then practice for the day you may need to DO it. If you are unwilling to end a life, don’t buy them in the first place.
The built in settings will take you pretty far. The obvious items are… Turn off unnecessary radios. NFC, Bluetooth, wifi, or cell. That will shut down parts of the phone that use material amounts of power. Shutting network points down should quiet some of the background processes that drains power on the phone. There are also built in functions to limit what apps can run in the background. Kill all your background processes you don’t absolutely want. Turn your screen all the way down. Have backup battery power available, it’s cheap and plentiful. No reason not have a 12v usb power supply in your car and a backup USB battery at home. A car battery can keep a phone running for weeks to months, with a gas tank to draw on you could probably run your phone for a year (if you did nothing else with your car). If you have the funds, a “solar generator” style power supply+battery will also keep it running for weeks to months with a minimum of fuss.
I would advise owning a pistol first. Pistols are small and can go places you can’t take your rifle. They are much more convenient for EDC, even within your home. Long periods of the potential to encounter hostiles are much more likely than a known certainty of hostiles. But this thread is about rifles… This is what I would do. Go to a few local gun stores, they will have items that are legal locally without needing to research all the laws. Find rifles that have the highest capacity for ready ammunition. Preferably with external magazines. Baring external mags, something like an SKS – a semi-auto with an internal mag that can be quickly reloaded is the next best bet. Avoid rimfire for defensive purposes. I’m not as familiar with the non-automatic options out there. But the general rule of highest capacity of ready ammunition is pretty sound.